PCB Exposure Box

date:June 10, 2010

PCB Exposure box

This summer I finaly decided to start making my own PCBs. The preferred method for making PCBs at home is photolithography. The PCBs used have a layer of photo resist, which is exposed to a source of light through a mask. The exposed areas are then removed using a special developer chemical. Lastly, the PCB is dipped into the etchant and the copper is removed from the areas unprotected by the photoresist.

The first thing I needed was a light source. I decided to build a small box for exposing my PCBs.

3D modeling

I began by creating a 3D model of the box usign Google Sketchup. This allowed me to spot any mistakes and tailor the design to suit my needs.

_images/exposure-box-model.png

Bill of materials

I used the following parts to make this box:

  • Chipboard
  • Plexiglass for the window
  • Fluorescent lamp
  • Reflector from some old lamp
  • IEC socket and cable
  • Power switch
  • Latch
  • Pair of hinges
  • Sponge cloth
  • Screws, glue

Results

Below is the picture of a test PCB. The safe limit of track width seems to be around 0.2-0.25mm. This could be influenced by the source of light. While experimenting with the timing, I got an impression that UV light could do a better job as it would allow reduced exposure times.

PCB test

Track widths from top to bottom are:

  1. 1.27mm
  2. 0.64mm
  3. 0.38mm
  4. 0.25mm
  5. 0.20mm
  6. 0.15mm
  7. 0.10mm

Table Of Contents

Previous topic

PIC Prototyping Board

Next topic

FPGA Based VGA Driver and Arcade Game

This Page